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Transparent thin-film transistors with zinc indium oxide channel layer

TitleTransparent thin-film transistors with zinc indium oxide channel layer
Publication TypeJournal Article
Year of Publication2005
AuthorsDeHuff, N. L., E. S. Kettenring, D. Hong, H. Q. Chiang, J. F. Wager, R. L. Hoffman, C. - H. Park, and D. A. Keszler
JournalJournal of Applied Physics
Volume97
Issue6
Pagination064505
Date Published2005
ISSN00218979
Keywordsamorphous semiconductors, annealing, electrical conductivity, electron mobility, high electron mobility transistors, indium compounds, semiconductor thin films, thin film transistors, visible spectra, wide band gap semiconductors, zinc compounds
Abstract

High mobility, n-type transparent thin-film transistors (TTFTs) with a zinc indium oxide (ZIO) channel layer are reported. Such devices are highly transparent with ∼ 85% optical transmission in the visible portion of the electromagnetic spectrum. ZIO TTFTs annealed at 600 °C operate in depletion-mode with threshold voltages −20 to −10 V and turn-on voltages ∼ 3 V less than the threshold voltage. These devices have excellent drain current saturation, peak incremental channel mobilities of 45–55 cm² V-¹ s-¹, drain current on-to-off ratios of ∼ 10⁶, and inverse subthreshold slopes of ∼ 0.8 V/decade. In contrast, ZIO TTFTs annealed at 300 °C typically operate in enhancement-mode with threshold voltages of 0–10 V and turn-on voltages 1–2 V less than the threshold voltage. These 300 °C devices exhibit excellent drain–current saturation, peak incremental channel mobilities of 10–30 cm² V-¹ s-¹, drain current on-to-off ratios of ∼ 10⁶, and inverse subthreshold slopes of ∼ 0.3 V/decade. ZIO TTFTs with the channel layer deposited near room temperature are also demonstrated. X-ray diffraction analysis indicates the channel layers of ZIO TTFTs to be amorphous for annealing temperatures up to 500 °C and polycrystalline at 600 °C. Low temperature processed ZIO is an example of a class of high performance TTFT channel materials involving amorphous oxides composed of heavy-metal cations with (n−1)d¹⁰ns⁰ (n ≥ 4) electronic configurations.

DOI10.1063/1.1862767
Short TitleJ. Appl. Phys.